This invention relates generally to device for measuring thicknesses of material, and, in particular, relates to a device for measuring turbine blade and vane clearances to other radially directed surfaces.
In a turbine engine, in an axial flow compressor section, in particular, a rotor shaft has attached thereon a plurality of rotor blades. The blades are positioned in circumferential rows that are spaced apart. Between these rows are located stator vanes, non-rotating, attached to the compressor case. The tips of the rotor blades and the tips of the stator vanes come in close proximity with the compressor case or the rotor shaft, respectfully.
During maintenance, these radial clearances are required to be determined to calculate whether the blades or vanes require replacement. To do such, small rectangular wax strips are attached between these critical areas and the rotor rotated a few rotations to cause the tips to remove the interferring wax of the wax strips. The remaining wax strip height thus indicates the clearance.
In the past, these wax strips were removed and measured with a micrometer. Although this procedure accomplished the desired result, the wax strips could become deformed during removal. This required that each strip be handled with great care, and since many strips are used to test one turbine engine, this procedure involved many additional hours of labor and possible erroneous results costing in labor and new blades or vanes being installed.
These drawbacks have motivated a search for alternative devices and procedures.